The method of hydroformylation to prepare aldehyde by reacting olefin with carbon monoxide and hydrogen are employed widely in industry, for example, in connection with monoolefins.
However, with regard to diolefins, such instance is few. For example, in Japanese Laid-Open Patent Publication Nos. 58-210033 and 59-110643, 5-ethylidene bicyclo[2.2.1]heptene-2 having two carbon-carbon double bonds is reacted, however, it is disclosed that formyl groups are introduced into the two unsaturated groups of the compound. In the same references, a formyl group is introduced into one of the unsaturated groups by regulating the amount of hydrogen and carbon monoxide to be used.
The inventors of the present application have found out that, with regard to specific diolefins, a formyl group is introduced into only one of the unsaturated groups under specific conditions, thereby accomplishing the present invention.